Question

有H2SO4和HCl的混合溶液20mL,加入0.025mol・L-1Ba（OH）2溶液时,生成沉淀的质量w

Answer 1

H2SO4+Ba(OH)2=BaSO4↓+2H2O

n(H2SO4)=n[Ba(OH)2]==0.025×0.020

c(H2SO4)=0.025mol/L

C点时混合溶液pH=7,说明正好中和

2n(H2SO4)+n(HCl)=2n[Ba(OH)2]

2×0.025×0.020＋c(HCl)×0.020＝2×0.025×0.060

c(HCl)＝0.100mol/L

A点:n(H+)=0.100mol/L×0.020L=0.002mol

c(H+)=0.002/0.040=0.05mol/L

pH=-lg0.05=2-0.7=1.3

B点:n(H+)=0.001mol

c(H+)=0.001/0.060=(0.1/6)mol/L

pH=-lg(0.1/6)=1+2lg3=2